To upgrade Firefox, you can read Update Firefox to the latest version. You should be able to update to Firefox 15.0.1. As for Quickbooks, does that even support Linux? After updating Firefox I would contact quickbooks support if you are still having trouble.

To upgrade Firefox, you can read [[Update Firefox to the latest version]]. You should be able to update to Firefox 15.0.1. As for Quickbooks, does that even support Linux? After updating Firefox I would contact quickbooks support if you are still having trouble.